Dielectric and piezoelectric properties of highly (100)-oriented BaTiO3 thin film grown on a Pt/TiOx/SiO2/Si substrate using LaNiO3 as a buffer layer

BaTiO3 thin films were deposited onto a Pt/TiOx/SiO2/Si substrate via the chemical solution deposition method, with LaNiO3 as a buffer layer. Effects of the concentration of precursor solution and LaNiO3 buffer layer on crystallinity and orientation, degree of BaTiO3 thin films have been investigated. At 0.2mol/l concentration, X-ray diffraction analyses show that the BaTiO3 films are highly (10 0)-oriented. The crystalline quality of BaTiO3 is significantly improved with LaNiO3 as a buffer layer. Smooth surface with evenly distributed grains as small as about 80 nm were observed by atomic force microscope. The electrical properties of the (10 0)-oriented films prepared by the one-step chemical solution deposition process have been studied. BaTiO3 thin films with a thickness of about 140 nm show a dielectric constant of similar to 340 and a loss tangent of similar to 2.9%. The BaTiO3 films show a good insulative characteristic against the applied field. The introduction of LaNiO3 buffer layer will decrease the onset of the high current emission of BaTiO3 films. A piezoelectric coefficient of 30 pm/V has been detected by the atomic force microscope on the bare film, which is twice as large as that of BaTiO3 thin film with random orientation. These results indicate that the highly (10 0)-oriented BaTiO3 should be a promising candidate as the lead-free thin film piezoelectrics. (c) 2005 Elsevier B.V. All rights reserved.